New inhibitors of protein kinase activity are urgently needed both as potential therapeutics for the treatment of conditions resulting from constitutively active signaling pathways and as tools for assigning function to kinases in diverse cellular contexts. While there are currently tremendous efforts to develop therapeutic kinase inhibitors by the pharmaceutical industry, the focus is predominantly on a small number of kinases that have been linked to disease. Therefore the vast majority of kinases are still not targeted by an inhibitor with a useful level of selectivity. Our long term objective is to generate narrow spectrum kinase inhibitors that will be able to inhibit all tyrosine kinases in the human genome. Recently, crystallographic analysis has revealed that a subset of kinase inhibitors bind and stabilize an inactive conformation of the kinase. We have developed and validated a pharmacophore model which will allow us to synthesize new inhibitors of kinase activation with selectivity profiles unique to all currently known kinase inhibitors. The specific aims of this grant are to deliver exploratory libraries of novel inhibitors of kinase activation to the Molecular Libraries Screening Center Network (MLSCN). In parallel, we will use a panel of cellular and enzymatic kinase assays to assign the kinase selectivity to all the new compounds that we prepare. Researchers who run assays at the NIH screening centers and find "hits" from these libraries will be able to use the annotated kinase selectivity profiles to generate immediate hypotheses regarding the kinases that maybe relevant to their particular assay of interest. We are preparing new inhibitors of proteins called kinases that are responsible for transmitting signals inside of human cells. Because many diseases are caused by kinases being turned "on" when they should not be, it maybe possible to treat these diseases by making inhibitors that can switch kinases off.